sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Texture: fine-grained; Cleavage: none in bulk rock form; Reaction: effervesces strongly with dilute acid.

Hardness: 3 on Mohs scale
Color: typically white, gray, or tan
Luster: dull to earthy

Identified June 2, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Texture: fine-grained; Cleavage: none in bulk rock form; Reaction: effervesces strongly with dilute acid.

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. It can also be formed by the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Extensively used in construction as an aggregate, cement manufacturing, soil conditioner in agriculture, and as a filler in products like toothpaste and paint.

Geological facts

Limestone is the primary stone used in the construction of the Great Pyramids of Giza. It is also the main rock type that forms karst topography, which includes caves and sinkholes.

Field identification & locations

Identify in the field by testing with a drop of vinegar (weak acid); it will bubble. Common in regions that were once prehistoric seafloors. Look for small fossil fragments.